I once rented this movie from Blockbuster back in the late 80s or the early 90s one. I think it was a Sinbad film (Sinbad as in the sailor, not the comedian). Anyway, I can't remember the plot very much, except for the fact that the main villain is unkillable because his heart is in a tower somewhere, and in order to vanquish him Sinbad has to get to this tower and stab his heart, and there's giant alligators and a dragon he has to fight, as well as a giant glove/gauntlet thing which guards the tower. I also remember him fighting an invisible monster in an arena earlier in the film.